Phosphoenolpyruvate carboxykinase is being purified from infant livers of SIDS victims. The purified enzyme from these livers will be compared with each other and other human liver samples as to electrophoretic properties in the absence and presence of sodium dodecyl sulfate, catalytic properties, and sensitivity to inactivation by selected chemical agents that differ in their modes of inactivation and properties when incorporated into the enzyme. These studies are designed to detect possible inherent differences in SIDS PEPCK, and possibly to provide information as to why the enzyme is present on autopsy in low amount.